pciutils: Add the support for a DOS/DJGPP environment

pciutils: Add the support for a DOS/DJGPP environment

Here is bit a blast from the past. The flashrom still supports the DOS/DJGPP environment, which requires
pciutils to be compiled with DJGPP. I originally developed this patch in 2010,
and I respun it for latest pciutils.

* Add DJGPP as an OS target
* Stop if endianess macros are not defined
* Introduce new intel_io_lock/unclock function to synchronize
  I/O operations.

There is a small issue left that "lspci" and "lspci.exe" are created. The ".exe" variants
are not installed and also not cleaned. No idea if you want to fix that or not.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Compiled with:

 make ZLIB=no DNS=no HOST=i386-djgpp-djgpp CROSS_COMPILE=i586-pc-msdosdjgpp- \
     PREFIX=/ DESTDIR=$PWD/../libpci-libgetopt  \
     STRIP="--strip-program=i586-pc-msdosdjgpp-strip -s" install install-lib

If you put to C:\share\pci.ids file, the lspci.exe will also display the human readable output.